1. Field of the Invention
The present invention relates to a working machine capable of improving the efficiency of a dredging operation on the bottom a shallow water area, such as a river, while maintaining safety in the operation.
2. Description of the Related Art
Conventionally, working machines capable of traveling both on land and on the bottom of the water, such as a riverbed, are known. The working machine of this type has an operator's cabin mounted at a position above a traveling means including a pair of endless tracks, for instance. In this cabin, the operator performs a predetermined controlling operation, thereby permitting the operation of an excavating means including a shovel, or other similar means.
However, even though the operator's cabin is located above the traveling means, in the case of a working machine in which the operator's cabin is located at a relatively low position, it is impossible to effect an operation in a river or the like whose depth of water is exceedingly large.
Accordingly, it is conceivable to render the heightwise position of the operator's cabin variable. However, working machines of a conventionally known type are arranged such that when the height of the operator's cabin is changed, a plurality of kinds of columns of varying lengths are provided in advance, and the column is replaced, as required, by an appropriate column prepared in correspondence with the depth of a river or the like, so as to change the height of the operator's cabin.
With this conventional type, in order to move the operator's cabin in the heightwise direction, it is necessary to replace the column with an appropriate one of the plurality of kinds of columns in correspondence with the depth of the river or the like. This replacement operation imposes a large burden on the operator since the weight of the operator's cabin including a power unit such as an engine is large.
In working machines of another type in which the column has a plurality of cylindrical pipes fitted one within another and is telescopically extended or retracted, the operator's cabin is lifted by an external device to set the telescopically extendible column to a desired heightwise position, and the column is then secured by means of bolts and nuts, lock pins, or the like.
Even with this conventional type in which the column is comprised of a plurality of tubular portions and is adapted to be telescopically extended or retracted in the longitudinal direction, if the machine is of a type in which the column itself cannot be automatically extended or retracted telescopically, the following drawback is encountered. That is, in order to set the operator's cabin and the power unit, such as the engine, from a state adapted for a land operation to a state adapted for an operation on the bottom of the water, or vice versa, it is necessary to lift them up by means of a separate crane or the like and then fix the column, with the result that the operation requires time and labor.
In addition, with the working machines of the above-described types, since not only the operator's cabin and the power unit but also a working boom with a bucket or the like and a balance weight are located in the upper position, the center of gravity becomes high during operations on the bottom of the water. As a result, there has been the drawback that the working machine is liable to become unstable.
To transport the dredged material, such as gravel, sand, and mud (hereinafter the dredged material will be simply referred to as the dredged gravel), excavated by the excavating means to land, the dredged gravel is generally stored temporarily on a barge or the like floating on water and adapted to transport the dredged gravel, and the barge is brought alongside the pier or the like to discharge the dredged gravel. In the operation of transporting the dredged gravel by using the barge, however, the barge carrying the dredged gravel stored temporarily thereon must reciprocate between the work site and the location where the barge is brought alongside the pier or the like. Then, the dredged gravel is discharged from the barge onto the land by using a separate shovel loader, crane, or the like. Thus the operating efficiency has been very poor.
In the operation of transporting the dredged gravel by means of the working machine capable of traveling on the bottom of the water, the direction of a traveling structure needs to be changed in correspondence with an operating condition when the dredged gravel excavated by the excavating means is discharged onto a load carrying platform, or when the dredged gravel is transported to the land. However, there frequently occur cases where the direction of the traveling structure is difficult to change on the bottom of the water owing to such conditions as the contours of the bottom of the water, the volume and velocity of flowing water, and so on. Hence, the operating efficiency has been very poor, and the danger involved in the operation has been large.
In the case of a working machine in which a load receiving means is juxtaposed to the operating cabin at a position above the traveling means, a predetermined position of the center of gravity of the entire working machine changes with an increase in the volume of gravel or the like loaded on the load receiving means. Hence, there has been the problem that the traveling stability becomes aggravated with an increase in the load.